Digital dermatitis (DD) is a contagious claw disease causing lameness in cattle, most commonly seen in intensive dairy production. The disease was first described in 1974 in Italy. In Sweden the first herd with DD was described recently (Hillström and Bergsten, 2005) whereas previously only sporadic, atypical cases have been reported (Manske et al., 2002). There is a strong connection between wet/dirty claw environments and the occurrence of DD (Rodriguez-Lainz et al., 1996), for example in cubicle systems where accumulation of faeces and urine on the alleys is a typical hygienic problem. Besides being an animal welfare problem, economic losses due to reduced milk production and weight loss are associated with DD (Losinger, 2006).
The rapid response to antibiotic treatment of DD lesions strongly supports a bacterial cause. Many bacteria of different genera, such as Treponema, Fusobacterium, Dichelobacter, Prevotella, and Porphyromonas have been isolated from DD lesions and a polymicrobial cause is often discussed. However, there is strong circumstantial evidence that Treponema spp. are central in the aetiology of DD. As early as 1964 spirochetes were observed in smears from different variants of “foot-rot” manifestations in cattle (Gupta et al., 1964). Another early observation of spirochetes was made 1988 when DD was described for the first time in the UK (Blowey and Sharp, 1988). The first spirochete cultures from DD were reported 1995 (Walker et al., 1995). In histological preparations from DD lesions treponemes are found invading the deeper layers of epidermis (Moter et al., 1998). Additionally a humoral immune response against Treponema spp. has been demonstrated in infected cattle (Walker et al., 1997; Trott et al., 2003). Successful experimental transmission of the disease through inoculation with fresh scrapings from DD lesions was described in 1996 (Read and Walker, 1996). It was also confirmed by histopathology that spirochetes invaded the tissue 1-2 weeks after inoculation (Read et al., 1998).
Several phylotypes of Treponema can be present in the same lesion. Different phylotypes have been isolated from the same animal (Walker et al., 1995; Evans et al., 2008) and by cloning and sequencing of 16S rRNA genes, five different phylotypes were identified in a pooled sample from four cows (Choi et al., 1997). It has also been demonstrated by fluorescence in situ hybridization on biopsies from DD lesions that the distribution in the dermal layers differs between phylotypes (Moter et al., 1998). The Treponema phagedenis-like phylotype was located mainly in the stratum corneum and stratum spinosum. Some phylotypes have not yet been reported as cultured. Recently the Treponema phagedenis-like phylotype has been indicated in several studies to be a key agent in the pathogenesis of DD (Klitgaard et al. 2008, Nordhoff et al. 2008, Yano et al. 2009).
In countries where DD is widespread, footbaths containing antibiotics are often used. These footbaths rapidly become contaminated with faeces and dirt and hence function as large selective cultures of antibiotic resistant bacteria. In Sweden tetracyclines are used, but only for topical treatment of individual animals since on herd level footbaths with copper sulphate are recommended.
To date no commercial vaccine or serologic test for DD is available. A humoral response against Treponema spp. has been shown in cattle with DD and used for whole cell lysate ELISA investigations in research (Demirkan et al. 1999, Trott et al. 2003, Vink et al. 2009, Walker et al. 1997). Novartis produced a whole cell lysate DD vaccine (TrepShield) for the USA market for some years in the early 2000s (Berry et al. 2004, Keil et al. 2002).
Technologies and strategies for development of vaccines are described in i.a. Vaccine Design: Innovative Approaches and Novel Strategies (Caister Academic Press, 2011) and Vaccines: From Concept to Clinic: A Guide to the Development and Clinical Testing of Vaccines for Human Use (Informa Healthcare, 1998). The use of a recombinant protein as a vaccine is described in Erdile et al. 1997.